The thin layer coating of substrates with dilute solutions of diblock copolymers has been the subject of considerable academic interest. For example, a recent paper by Budkowski et al provides a description of the phenomena that are speculated to occur when an A-B type block copolymer is used to coat a substrate, namely that one of the blocks (for example, block A) attaches to a surface and that the other block (ie. block B) ". . . dangles out to form a brushlike layer . . . " (Budkowski et al, Macromolecules 1993, 26, p2470). Budkowski et al further describes the use of such A/B block copolymers to improve the interface between a layer of homopolymer A and homopolymer B (ie. in such applications, the A/B block copolymer layer is sandwiched between a layer of homopolymer A and homopolymer B).
The use of diblock copolymer to provide a thin coating is of potential commercial interest. However, the simple deposition of a diblock copolymer on a substrate leaves a very thin layer coating which is subject to ready attack (for example, it may be easily dissolved away, or abraded or attacked by an acid/base). Whilst the problem of this type of attack may not be severe in the application describe by Budkowski et al (because the thick layer of the AB diblock is "protected" by a layer of homopolymer A and a layer of homopolymer B), it presents a substantial problem if the coating is to be exposed. It is an object of the present invention to address this problem by employing a process which provides a thin layer of crosslinked copolymer on a substrate.